It's once a year and in general I'd say they are tougher than SAT.
Here is what I know back then as a student who took GaoKao in the 90s:
1. GaoKao also has provincial variants.
For example, back in the year when I took GaoKao, my city used a form called "3+1", which means 3 primary (Chinese, Math and English) plus 1 auxiliary. You can choose the auxiliary at the end of 11th grade, and the choices are Politics, History, Biology, Physics, Chemistry, etc. Other provinces used different forms but the majority were and still are on "3+2", so instead of one auxiliary they have to prepare for two.
From what I recalled, a few years after some provinces switched to 3+X (X depends on your choice). You still only get 1 exam for the X though.
2. Different universities have different entry scores for different provinces.
For example, I got a score of 420/600 I think? The university I went to actually charged different entry scores for different provinces. It makes sense in one way, as different provinces have different forms of GaoKao, but overall it's very unfair to students from less developed areas. I won't expand the reasoning from here but it has been a huge debate since decades ago.
Here is what I know back then as a student who took GaoKao in the 90s:
1. GaoKao also has provincial variants.
For example, back in the year when I took GaoKao, my city used a form called "3+1", which means 3 primary (Chinese, Math and English) plus 1 auxiliary. You can choose the auxiliary at the end of 11th grade, and the choices are Politics, History, Biology, Physics, Chemistry, etc. Other provinces used different forms but the majority were and still are on "3+2", so instead of one auxiliary they have to prepare for two.
From what I recalled, a few years after some provinces switched to 3+X (X depends on your choice). You still only get 1 exam for the X though.
2. Different universities have different entry scores for different provinces.
For example, I got a score of 420/600 I think? The university I went to actually charged different entry scores for different provinces. It makes sense in one way, as different provinces have different forms of GaoKao, but overall it's very unfair to students from less developed areas. I won't expand the reasoning from here but it has been a huge debate since decades ago.